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Brake Problem

Discussion in 'General Technical / How To' started by Gnasher, Oct 25, 2007.

  1. Gnasher
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    Gnasher Gansher

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    [Oct 25, 2007]
    Strange brake problem - Near side brake sticking, thought it was a sticky cylinder. ok for a few days after apparently unsticking and now the brakes feel very spongy at first and the brake peddle has lots of play at the start of a journey but throughout the journey they become more firm untill eventually the near side rear decides to stick on again. left the car for a while and brake releases its self? But Same thing keeps happening ok on journeys without much braking but lots of stopping and starting it soon returns. Yesterday the near side rear was completely siezed on so took wheel off and loosened bleed nut to let a small amount of fluid out and brake instantly released, making me believe its not a sticky cylinder problem?
    Can anybody help? do i need to complety rebleed the whole system or is it gonna be an expensive stealer repair?

    oh its an 1999 A6 Quattro 2.5tdi Avant.
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  3. enda1
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    enda1 Member

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    [Oct 25, 2007]
    I had a similiar problem on my audi 80 with the front driver side brake, and by letting out a small amount of fluid it would temporarily solve the problem. I bleeed the whole system and problem never came back
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  4. Caesium
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    Caesium My BM is fixed!

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    [Oct 26, 2007]
    Unlikely to be a sticky cylinder as the brakes are most likely to be discs.
    Have you had the fluid changed in the last 2 years? Its supposed to be changed every 24 months. It goes a bit crappy after a while.
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  5. Gnasher
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    Gnasher Gansher

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    [Oct 28, 2007]
    I decided to replace the old fluid with fresh new fluid and have come across another problem - No fluid coming out of the rear right which is the opposite side where i was having problems before.

    After further investigation it appears that there is nothing coming from the rear hole of the Master Cylinder even with thepeddle depressed and a gunson pressure bleeder attached to the fluid container.

    I am now thinking that this is a master cylinder problem? and have little or no braking power at all.
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  6. shineydave
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    shineydave Member

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    [Oct 28, 2007]
    if it's rear discs and the is handbrake incorporated into the calliper i'm 99% certain it's the handbrake mechanism causing the prob. it'll only be one calliper causing the problem but i always do both as sooner or later the other one will go so you might as well do it now while you have all the kit to hand.

    basically the levers that attach to the handbrake cable have to return to the stop when the lever is released, if they don't then everytime you press the brake pedal the piston "adjusts" up a bit more, eventually it can't adjust anymore and is firm against the disc.

    first, remove the cable and check that it's free to move, if not you'll need to replace them, only cheap from the likes of German and Swedish.

    next step is to free the levers on the callipers, i find the easiest way is to remove the 10mm nut that holds the spring in place, whip the spring off and then, using plenty of lube work the leaver back and forth. if you push it right back to the stop you'll be able to lever it up out of the calliper body too to get more lube in there. don't worry about it coming out, it's held from within.

    once you have BOTH levers working properly you need to reset the pistons in the calliper, these need to be pushed in and rotated clockwise at the same time to reset the handbrake adjuster, you can buy a special tool for this for about £20. once you have the pistons all the way back and the cables connected check that both cables have adequate slack in them by pushing the lever on one calliper to the stop then check the other lever is still on the stop. if pushing one lever to the stop pulls the other one off then the cable is too tight, i always leave plenty of slack in there anyway as often the limited travel on the cables can cause them to sieze, more is better.

    once you're happy that the cables are good, the levers are both free and on the stops and the pistons have been correctly rotated to reset the handbrake then you need to drop the car back onto it's wheels (as you need the weight of the car to open the brake pressure limiting valve on the back axle) it's now just a simple matter of pumping the brake pedal anything between 3 and 30 times to reset the handbrake. the key thing here is to have enough slack in the cable to allow both levers to return to the stops.

    hope that helps

    PS: the reason no fluid comes out of the nipple is because you've jacked the car up by the bodywork allowing the rear axle to drop, this closes the brake pressure compensating valve and stops the fluid flowing
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  7. shineydave
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    shineydave Member

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    [Oct 28, 2007]
    ooops, mis-read your previous post about no fluid, thought you meant out of the calliper, the rest is still valid though
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  8. Gnasher
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    Gnasher Gansher

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    [Oct 28, 2007]
    Thanks for that info, handbrake works ok and both levers are returning to the required stop.

    But i dont have anything coming out of one of the master cylinder holes one nearest the servo which means there is no fluid flowing to the ABS control unit and then nothing to the brake line? hence me thinking it's the Master cylinder. Peddle goes straight to the floor after pumping it a bit there feels like something is there and then it seems to drop all of a sudden after about halfway down. Oh and the ABS light is on too!!

    I think i'll have to take it to the garage as it needs to be sorted as it is the brakes. Tax due end of month MOT due in two weeks too!! its gonna be an expensive month. get paid on Wednesday!
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  9. maverick
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    maverick New Member

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    [Dec 3, 2007]
    I have an audi 80 sport someone cut my brake line on the driver side not a problem just fitted a new part fine but I can not get any brake fuild out of the driver side rear calaper can someone help me please the ABS light goes off and the brakes are not very good at all well no pressure at all:lmfao:
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  10. shineydave
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    shineydave Member

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    [Dec 3, 2007]
    are you jacking it up on the body? if you are the axle will be hanging down causing the brake pressure limiting valve to close so no pressure will get to the rear callipers, try jacking it up on the axle
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  11. maverick
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    maverick New Member

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    [Dec 4, 2007]
    was jacking up on the body but did have fluid comming from the rear passenger side but have since found out the abs pump has gone
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  12. Gnasher
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    Gnasher Gansher

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    [Dec 5, 2007]
    Mine was the master cylinder, and the ABS ECU had gone up the spout to got a refurbed ECU but am still getting Orange ABS light on dash.....cant get MOT till i get this sorted :no:

    I think it may be the ABS speed sensors now. Does anyone know if VAG.COM will operate on Vista? and can i diognose any faults with the free version?
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  13. Gnasher
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    Gnasher Gansher

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    [Dec 17, 2007]
    I am now starting to get pissed off. New Master cylinder, refurbed abs ecu, new abs speed sensors. and now garage is telling me that they are getting fault code 65535 ABS control module?????????????????

    So ok what can it be now refurbed ecu up spout? bad connection?

    Help please as been borrowing cars since end of October.
    Starting to think it needs to goto the stealers?

    Just got a Bike (but its a bit cold to ride 25 miles to work each day at moment :cold: ) hopefully car will be better soon!!

    Need help!!
    #12

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